Shackleton had been warned of severe sea ice conditions and an unusually long season of cold weather in Antarctica, so he delayed his departure for a month, finally setting sail for Vahsel Bay in early December 1914. Shackleton hoped to find some way around or through the sea ice in summer, for he needed to reach land in time to set up winter quarters.

Remember that winter comes to Antarctica in June. This is when the South Pole begins to point away from the Sun as Earth, tilted on its axis, makes its orbit around the Sun. As winter progresses, the Sun's rays strike Antarctica at lower and lower angles, providing less and less energy per square kilometer. Temperatures drop. It gets so cold that the ocean begins to freeze, forming sea ice. Sea ice continues to form throughout the winter months. As the ice forms it moves northward, creating regions of open water that then freeze and form more sea ice. Eventually, the ice extends over millions of square kilometers of ocean around Antarctica.

Sea ice tends to keep Antarctica cold even in summer. How does it do that? Two properties of sea ice come into play. First, sea ice is highly reflective. Second, sea ice provides insulation between the ocean and the atmosphere. Because of something called positive feedback, the more sea ice there is in Antarctica, the colder the climate tends to remain.

In this investigation, you will explore how reflectivity and insulation affect the transfer of heat energy. You will also learn more about positive feedback. When you are done, you will have a better idea of how sea ice and climate are related and why Shackleton had so much trouble with sea ice in Antarctica.

Goals

1. You will see how reflectivity and insulation affect heat transfer.
2. You will learn how sea ice reflects sunlight and insulates the ocean from the air, keeping Antarctica cold.
3. You will discuss some historical evidence that suggests there has been a recent climate change in Antarctica. You will also discuss sea ice's role in global climate change.